Design, Construction, and Maintenance of Bridges

Numerical analysis method was presented in this paper to solve the response of the vehicle-bridge coupled vibration. In this method the bridge model and vehicle model were set up separately in the ANSYS environment. Then the relationship of the response of the coupled vibration was calculated by APDL language. Finally the vibration time response was obtained by imposing the coupled relationship on vehicles and bridges at any time. This method proved to be reasonable by comparing with existing literature and experimental results. This paper also presents the judging method and formulas of the response of the coupled vibration based on the conditions of single vehicle and multivehicles driving on the continuous rigid frame bridge and raised the judging models for resonance of different driving conditions. The results are in good agreement with the facts. The results showed that continuous rigid frame bridges are likely to cause response of resonance under the conditions of a single vehicle and equally spaced traffic flow. The load effect of the pier increases much more sharply than that of the main girder when the resonance occurs. Based on the results of this paper, it is suggest that disrupting the traffic flow by setting the deceleration traffic signs at the different longitudinal position on the bridge deck is an effecctive way to decrease the frequency of the resonance of the continuous rigid frame bridges.

Falling accounts for the majority of accidents in a bridge construction project. Site safety management today relies on checklist assessment, which is dependent on the ability and experience of the evaluators. In addition, the method used to carry out site safety management today could not address the most critical factors that lead to site accidents. To go beyond the limitations of the traditional checklist method, in this study the factors of falling in construction site are analyzed in a Fault Tree (FT), and then the FT is transformed into a Bayesian Network (BN). The BN enables us to explore the probabilities of accidents happening. When compared with current cases of bridge construction in Taiwan, it is worth noting that the result from the BN model agrees with the result from traditional checklist method. In other words, the BN model was verified to be a realistic and useful model to deal with site safety management problems.

A probabilistic methodology is developed in this paper for identifying the most effective way to install a limited number of sensors on the continuous-coordinated system to extract as much information as possible. This is performed by minimizing the information entropy associated with the identified bridge modeling parameters. Although the commonly used discrete-coordinated systems (such as the finite element method) provide a convenient and practical approach to the dynamic response analysis of arbitrary structures, the solutions obtained can only approximate their actual dynamic behavior, because the motions are represented by a limited number of displacement coordinates. This would undoubtedly influence the precision of dynamical analysis results, which, in turn, influence the sensor configuration results. For bridge structures having typical distributed properties, it is more reasonable and accurate to be modeled as distributed-parameter system with analytical formulation. This is employed in this paper for investigating the sensor placement problem with the information entropy-based method through the numerical simulation of a three-span continuous bridge model.

To ensure the safety of the high-speed railway bridge influenced by the excavating and dewatering work of the underpass bridge, risk assessment research had been put into practice in Cuiheng Road underpass of the Beijing-Tianjin intercity railway. Combining the quantitative and the qualitative analysis, the fatality analysis method was introduced to acquire an explicit conclusion and for available suggestions. First, the risk sources, the probability of occurrence, and the approximate degree ofharm were researched by the specialist consultation and the risk committee. Aimed to find kernel risk sources, such as excavating and dewatering construction, the finite element models (FEMs)were used to acquire the deflections of the bridge foundation and the approach embankment in various conditions. The ALARP principle was introduced to determine the risk assessment results. Safety control means were researched, and the twin row waterproof curtain by jet grouting piles and full bottom sealing by soil-cement mixing piles were suggested to achieve the target of feebleness disturbed deflection. The ARIMA method was applied in the settlement forecasting, and the indicator system for a security alarm was suggested to those monitoring construction work.

Bridge seismic isolation technology provides an effective approach to improving the seismic performance of a bridge. An isolation-bearing device, which is widely adapted in bridge structure, has proved to be simple and effective. A three-dimensional finite element model (FEM) of a prestressed concrete long-span continuous girder bridge is established to analyze its dynamic characteristics. High damping rubber bearing isolation is used to reduce bridge structure vibration under seismic excitations. And seismic dynamic responses are analyzed by nonlinear time history method. It is shown that the seismic response of bridges can be decreased significantly by using damping bearings.

The strut-and-tie model is supposed to be a more appropriate design method for pile caps than the general flexural member approach. A new strut-and tie model, therefore, is put forward for caps with six piles including truss action, direct arch action, or a combination of both actions. In the model, comprehensive factors were considered such as selection of truss/direct arch/both actions, solution of pile reaction force, load type including concentrated, and distributed load, as well as distribution of pile reaction force and so forth. The designing and checking process was programmed by Matlab language. Designing methods of related node and calculations of inclined struts with variable cross-section are analyzed. Specific designing and checking methods about the struts, ties, and nodes are obtained after a comprehensive comparison. The new model proposed is validated by specific test cap samples with six piles. High accuracy is reached in computing the ultimate load and failure mechanism compared to corresponding test results. There is certain economy in reducing the amount of reinforcement and effectively utilizing all members.

Ultrasonic wave testing is a classic NDT method to detect, locate, and monitor the cracks and fractures in construction materials. In this paper, a new ultrasound data interpretation technique is introduced: The reverse time migration (RTM) is a wave equation-based prestack method used in seismic exploration. Because RTM can utilize all kinds of waves, such as reflection waves, refraction waves, and diffraction waves, it has no dip limits in migration and can create an image of the inside of complicated structures. However, the large data generation and sophisticated velocity field analysis are the bottlenecks for RTM that hinder its wide applications. A hybrid boundary condition (including random boundary and absorption boundary simultaneously) is suggested in this paper to reconstruct the source wave field to address the memory storage issues. A numerical model with S-shaped internal fracture is presented to demonstrate the technique for detection of internal flaws. The results indicate that the accuracy of detecting the embedded flaw within construction material is affected by the sampling space and the range of wave frequency.

This paper discusses advances in evaluation, health monitoring, and rehabilitation of cable-stayed bridges and available methods. In the last two decades, the author has contributed extensively to advances in cable-stayed bridge evaluation, inspection, and health monitoring. Information gathered from evaluation of the strength and reliability ofcable-stay systems for nearly 25 long-span bridges, and instrumentation, health monitoring, and inspection of more than 12 cable-stayed bridges in the United States and abroad has helped the formation of a unified approach for evaluation and problem solving of these aesthetic structures. A case study related to evaluation and rehabilitation of the Luling Bridge in Louisiana, for which the new approach has been implemented almost entirely, is also described. The bridge evaluation process and cable replacement design and its implementation contain unique aspects and are the first attempted in North America. The cable replacement design accommodated an extraordinary construction sequence to address constraints on space and traffic flow. The new cable system allows individual strand installation and tensioning and is expected to facilitate future inspections and replacement.

To effectively control the safety risk of existing subway viaducts and extend the service lives of subway viaducts, damages investigation of subway viaducts was implemented and the main causes of damages were analyzed. Based on investigation results and theory analysis, the functions degradation states of subway viaducts, which were divided into five stages of their lifetime, were put forward. To support the elementary object of sustaining subway viaducts' life, the modes of maintenance and safety management(MSM) of subway viaducts were discussed, and a closed mode of MSM, which is similar to the PDCA circle and can continuously improve the performance of subway viaducts, was set up. Further, the mode of MSM was promoted to manage and maintain the rail traffic facilities in the life cycle. The proposed new thought of MSM can provide reference for discussing MSM of other engineering structures.

To investigate the seismic behavior of RC columns reinforced with fine grain steel bars, four rectangle cross-section HRBF400 RC columns bending low-cycle reversed loading experiment were made. Effects of reinforcement ratio, axial compression ratio, and stirrup ratio on the seismic performance of RC columns were analyzed. Characteristic of hysteretic curve and skeleton curve were studied, and characteristic value and displacement ductility of each component were calculated. The results showed HRBF400 RC columns have good seismic behavior. With the increasing of reinforcement ratio, yield load, peak load, and ductility have correspondingly improved. Columns of high-compression ratio has high peak load and yield load, but its skeleton curve after peak load decreased fast and has low ductility. Columns of low compression ratio has low peak load and low load, but its skeleton curve after peak load decreased gently and has good ductility. Seismic behavior and ductility of RC columns were improved with the increasing of stirrup ratio.

This paper proposes four evacuation passageways from a high-speed railway bridge in mountainous areas. These are escape staircase, escape chutes, escape lift, and flexible slip pocket. Based on the characteristic of every evacuation passageway, the evaluation system is established. Four evaluation indexes are put forward in the system. They are escape efficiency, construction costs, safety index, and difficulty in level of operation. Then, the variable weight method is applied to calculate the indexes weights. Finally, a project case is given for comparison to validate the approach. The research shows that the variable weight theory can highlight the negative influence of some indexes and offer a scientific decision making of the evacuation passageway construction.

The effectiveness of emergency medical services (EMS) depends on the existing infrastructure and allocation of medical resources. It is, in general, considered that the response time for ambulances is a critical factor to the survival of major trauma patients. EMS is a challenging task due to the spatial distribution of the population and geographical layout in urban areas. The configuration of EMS units and hospitals should be assessed to provide an efficient service. In this research, the effect of disasters is considered as the disturbance of the EMS system. The objective of this research is to assess the service area of EMS after a disaster. In this study, the deviation of service area is observed before and after the disturbance on the transportation infrastructure disaster.